Steam generator reinforcement method and steam generator

Abstract

To provide a reinforcement method of a steam generator which can improve workability of the reinforcement of the steam generator and can reinforce a target area of an outside surface of a steam separator efficiently.SOLUTION: A steam generator comprises: a cylindrical body unit 2 extending in vertical direction; a heat exchange unit installed in the body unit; a water supply unit 4 installed above the heat exchange unit in the body unit; and a steam separator 5 installed above the heat exchange unit in the body unit. A reinforcement method of the steam generator reinforces a target area 51aA in the outside surface 51a of the steam separator where secondary cooling water supplied from the water supply unit hits, and includes: a preparation step preparing multiple patches 9 machined for a shape according to the target area of the outside surface in the outside of the body unit; a carry-in step carrying the multiple patches in the body unit; and a welding step welding the multiple patches carried in the body unit put on the target area of the outside surface and arranging along the target area.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a method for reinforcing a steam generator and a steam generator. [Background technology]

[0002] In a steam generator used in a pressurized water reactor (PWR) or the like, a heat exchange section is provided in the lower part of a cylindrical body section for cooling high-temperature primary cooling water from the reactor by heat exchange between the primary cooling water and the secondary cooling water. In addition, a water supply section for supplying secondary cooling water to the heat exchange section and a steam-water separator for separating the secondary cooling water, which is heated by the primary cooling water and rises in the heat exchange section, into steam and hot water, are provided in the body section above the heat exchange section. The water supply section discharges the secondary cooling water from the upper part of the heat exchange section in the body section. At this time, a part of the secondary cooling water hits a target area on the outer surface of the steam-water separator. If the secondary cooling water hits the target area on the outer surface of the steam-water separator for a long period of time, the target area will be thinned due to erosion or corrosion. Patent Document 1 discloses a repair method for when the main body shell of a moisture separator through which steam flows is thinned by the steam flow, in which a coating of a corrosion-resistant alloy is formed by thermal spraying on the thinned portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-219850 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the space in which the target area of ​​the outer surface of the steam-water separator that the secondary cooling water hits is located is narrow, so that thermal spraying of the target area of ​​the outer surface of the steam-water separator is difficult to perform, and it takes a long time to repair or reinforce the target area of ​​the steam-water separator.

[0005] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a steam generator reinforcing method and a steam generator that can improve the ease of reinforcement work and efficiently reinforce target areas on the outer surface of a steam-water separator. [Means for solving the problem]

[0006] In order to solve the above problems, the reinforcement method for a steam generator according to the present disclosure includes a cylindrical body portion extending in a vertical direction, a heat exchange portion provided in a lower portion within the body portion for cooling high-temperature primary cooling water by heat exchange between the primary cooling water and secondary cooling water, a water supply portion provided within the body portion above the heat exchange portion for supplying the secondary cooling water to the heat exchange portion, and a steam-water separator provided within the body portion above the heat exchange portion for separating the secondary cooling water, which is heated by the primary cooling water and rises in the heat exchange portion, into steam and hot water. a steam generator having a steam separator, the steam generator having a steam separator and a steam supply section, and a steam generator reinforcing section for reinforcing a target area of ​​the outer surface of the steam separator that is contacted by the secondary cooling water supplied from the water supply section, the steam generator reinforcing section comprising: a preparation step of preparing a plurality of backing plates processed into a shape that conforms to the target area of ​​the outer surface outside of the body; a carrying step of carrying the plurality of backing plates into the body; and a welding step of overlapping and welding the plurality of backing plates carried into the body to the target area of ​​the outer surface, and arranging them along the target area of ​​the outer surface.

[0007] The steam generator according to the present disclosure comprises a cylindrical body extending in the vertical direction, a heat exchange section provided in a lower part of the body for cooling high-temperature primary cooling water by heat exchange between the primary cooling water and secondary cooling water, a water supply section provided within the body above the heat exchange section for supplying the secondary cooling water to the heat exchange section, a steam-water separator provided within the body above the heat exchange section for separating the secondary cooling water that is heated by the primary cooling water and rises in the heat exchange section into steam and hot water, and a plurality of backing plates welded to a target area of ​​the outer surface of the steam-water separator that is hit by the secondary cooling water supplied from the water supply section and aligned along the target area of ​​the outer surface. Effect of the Invention

[0008] According to the present disclosure, the workability of reinforcement in a steam generator can be improved, and the target area on the outer surface of a steam-water separator can be efficiently reinforced. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic configuration diagram showing a steam generator according to an embodiment of the present disclosure. [Diagram 2] 2 is a diagram showing the relative positional relationship between the water supply part in FIG. 1 and a riser pipe of a steam-water separator, as viewed from above the water supply part. [Diagram 3] FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2. [Figure 4] FIG. 4 is a perspective view showing the riser pipe and a backing plate attached to the outer peripheral surface of the riser pipe in FIGS. [Diagram 5] FIG. 5 is a perspective view showing a first example of the backing plate of FIG. 4. [Figure 6] FIG. 5 is a perspective view showing a second example of the backing plate of FIG. 4. [Figure 7] 10A to 10C are diagrams showing a process of attaching a backing plate to an outer circumferential surface of a riser pipe in a method for reinforcing a steam generator according to an embodiment of the present disclosure. [Figure 8] 10A and 10B are diagrams showing an example of a method for pressing a backing plate against an outer circumferential surface of a riser pipe in the process of attaching the backing plate to the outer circumferential surface of the riser pipe. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <Embodiment> (Steam generator configuration) The steam generator 1 of this embodiment shown in Fig. 1 is applied to, for example, nuclear power generation facilities. In the steam generator 1, heat is exchanged between high-temperature primary cooling water heated in a nuclear reactor (not shown) and secondary cooling water supplied from the outside, and steam is generated from the secondary cooling water by heat exchange with the primary cooling water. Electricity can be generated by sending the generated steam from the steam generator 1 to a turbine generator (not shown). 1 to 4, the steam generator 1 includes a body section 2, a heat exchange section 3, a water supply section 4, a steam separator 5, and a plurality of backing plates 9. Moreover, as shown in FIG. 1, the steam generator 1 further includes a water chamber head 6 and a moisture separator 7.

[0011] (Torso) The body 2 is formed in a cylindrical shape extending in the vertical direction. The body 2 has a lower body 2a forming the lower half, an upper body 2b forming the upper half, a conical body 2c connecting the lower body 2a and the upper body 2b, and an upper mirror 2d provided at the upper end of the upper body 2b. The upper body 2b has a manhole 21 (entrance / exit) for entering and exiting the inside of the body 2. The manhole 21 is located at the top of the upper body 2b, but is not limited thereto. The size of the manhole 21 is, for example, large enough for a person to pass through. The upper body 2b is provided with a lid 23 for opening and closing the manhole 21. The upper body 2b has a slightly smaller diameter than the lower body 2a. The conical body 2c is formed in a substantially truncated cone shape so that the lower body 2a and the upper body 2b can be connected. The upper mirror 2d is formed with a steam exhaust port 22. A pipe (not shown) is connected to the steam exhaust port 22 for sending steam exhausted from the body 2 to a turbine generator.

[0012] A tube sheet 8 is disposed at the lower end of the lower body 2a. The tube sheet 8 closes the opening at the lower end of the lower body 2a. The tube sheet 8 has a plurality of tube holes 8a formed therein that penetrate in the vertical direction.

[0013] (Heat exchange part) The heat exchange unit 3 is provided inside the lower body 2a (the lower part of the body 2) and cools the high-temperature primary cooling water by heat exchange between the primary cooling water and the secondary cooling water. The heat exchange unit 3 has a tube bundle outer cylinder 31 (wrapper tube), a heat transfer tube bundle 32A, a tube support plate 33, and an anti-vibration member 34. The tube bundle outer cylinder 31 is formed in a cylindrical shape extending in the vertical direction. The tube bundle outer cylinder 31 is arranged at a predetermined interval from the inner circumferential surface of the lower body 2a. The lower end of the tube bundle outer cylinder 31 is located near the tube sheet 8 arranged at the lower end of the lower body 2a. The upper end of the tube bundle outer cylinder 31 is connected to the lower end of the riser pipe 51 of the steam-water separator 5.

[0014] The heat transfer tube group 32A is provided inside the tube group outer cylinder 31. The heat transfer tube group 32A has a plurality of heat transfer tubes 32 that are in an inverted U-shape and extend in the vertical direction. Each heat transfer tube 32 is arranged to extend from the upper end to the lower end of the lower body 2a with the circular arc portion of the U-shape facing upward. Both ends of each heat transfer tube 32 located on the lower end side of the lower body 2a are inserted and fixed into tube holes 8a in the tube plate 8. As a result, both ends of each heat transfer tube 32 open below the tube plate 8.

[0015] The tube support plate 33 is attached to the tube bundle outer cylinder 31 so that the plate thickness direction faces the up-down direction of the tube bundle outer cylinder 31. A plurality of tube support plates 33 are arranged vertically at intervals. The plurality of tube support plates 33 support the heat transfer tubes 32 at mid-way portions in the longitudinal direction. Specifically, the tube support plate 33 has a large number of heat transfer tube insertion holes 33a formed therein that penetrate in the plate thickness direction. The tube support plate 33 supports the heat transfer tubes 32 by inserting the heat transfer tubes 32 into the heat transfer tube insertion holes 33a.

[0016] The anti-vibration members 34 are inserted between the overlapping laterally arranged arc portions of the heat transfer tubes 32. The anti-vibration members 34 suppress flow-induced vibrations that may occur in the U-shaped arc portions of the heat transfer tubes 32 when the primary cooling water passes through the heat transfer tubes 32.

[0017] The heat exchange section 3 configured as above is formed with a flow passage 35. The flow passage 35 is formed so that the secondary cooling water supplied from the water supply section 4 into the lower body 2a flows down between the inside of the lower body 2a and the outside of the tube bank outer casing 31, turns back at the tube sheet 8, and rises inside the tube bank outer casing 31 along the heat transfer tube group 32A.

[0018] (Mizumuro Kagami) The water chamber head 6 is provided below the tube plate 8. The inside of the water chamber head 6 is divided into an inlet side water chamber 6A and an outlet side water chamber 6B. One end of each of the heat transfer tubes 32 is connected to the inlet side water chamber 6A. Meanwhile, the other end of each of the heat transfer tubes 32 is connected to the outlet side water chamber 6B.

[0019] The water chamber mirror 6 is formed with an inlet nozzle 6Aa that opens the inlet side water chamber 6A to the outside of the water chamber mirror 6, and an outlet nozzle 6Ba that opens the outlet side water chamber 6B to the outside of the water chamber mirror 6. The inlet nozzle 6Aa is connected to a pipe (not shown) for sending the primary cooling water from the reactor to the heat exchange section 3. The outlet nozzle 6Ba is connected to a pipe (not shown) for returning the primary cooling water after heat exchange in the heat exchange section 3 to the reactor.

[0020] (Water supply section) 1 and 2, the water supply section 4 is provided inside the upper body 2b (above the heat exchange section 3 within the body section 2). The water supply section 4 introduces secondary cooling water from the outside of the body section 2 and supplies it to the heat exchange section 3. The water supply section 4 has an annular water supply pipe 41 and a plurality of discharge pipes 42 (J tubes). The ring-shaped water supply pipe 41 is formed in a ring shape along the inner circumference of the cylindrical upper body 2b. An introduction pipe 43 is connected to the ring-shaped water supply pipe 41, which passes through the upper body 2b and introduces secondary cooling water from the outside into the ring-shaped water supply pipe 41.

[0021] 2, the multiple discharge pipes 42 are provided on the annular water supply pipe 41 so as to be arranged at intervals from each other in the circumferential direction of the annular water supply pipe 41. Each discharge pipe 42 discharges the secondary cooling water flowing in the annular water supply pipe 41 downward toward the heat exchange unit 3. As shown in Fig. 3, one end in the longitudinal direction of each discharge pipe 42 is connected to the annular water supply pipe 41. The other end in the longitudinal direction of each discharge pipe 42 is a discharge port 42b through which the secondary cooling water is discharged, and faces downward. Specifically, each discharge pipe 42 is curved in a J shape so as to extend upward from the upper end of the annular water supply pipe 41 and then turn back downward. The discharge port 42b of each discharge pipe 42 is located radially inside the annular water supply pipe 41.

[0022] (Steam water separator) 1, the steam-water separator 5 is provided inside the upper body 2b (above the heat exchange section 3 within the body 2). The steam-water separator 5 separates the secondary cooling water, which is heated by the primary cooling water in the heat exchange section 3 and rises, into steam and hot water.

[0023] The steam-water separator 5 has a cylindrical riser pipe 51 extending in the vertical direction. The lower end of the riser pipe 51 is connected to the upper end of the tube bank outer cylinder 31 of the heat exchange section 3. As a result, the secondary cooling water rising inside the tube bank outer cylinder 31 of the heat exchange section 3 passes inside the riser pipe 51. As shown in Figs. 1 and 2, the diameter of the riser pipe 51 as viewed from the vertical direction is smaller than the diameter of the annular water supply pipe 41 of the water supply section 4. The riser pipe 51 is arranged to pass inside the annular water supply pipe 41 in the vertical direction.

[0024] When viewed from the top-bottom direction, the riser pipe 51 is positioned close to the inner edge of the annular supply water pipe 41. For this reason, as shown in Figures 2 and 3, a part of the circumferential area of ​​the outer circumferential surface 51a (outer surface) of the riser pipe 51 is positioned close to the discharge port 42b of the discharge pipe 42 of the water supply section 4, and serves as a target area 51aA that is hit by the secondary cooling water discharged from the discharge port 42b. The angle range of the target area 51aA of the riser pipe 51 in the circumferential direction may be, for example, 170 degrees to 180 degrees, but is not limited thereto.

[0025] (Backing plate) As shown in Figs. 2 to 4, the backing plates 9 are welded to the target area 51aA of the riser pipe 51 in an overlapping manner. Each backing plate 9 is formed in a shape that conforms to the outer peripheral surface 51a of the cylindrical riser pipe 51 so as to be in close contact (surface contact) with the target area 51aA of the riser pipe 51. As shown in Figs. 4 to 6, the backing plate 9 is formed in a shape that is curved in an arc shape in one direction along the surface of the backing plate 9. Specifically, each backing plate 9 is formed in a curved rectangular shape having a pair of horizontal sides 9a extending along the circumferential direction of the riser pipe 51 and a pair of vertical sides 9b extending along the longitudinal direction (up-down direction) of the riser pipe 51. The size of each backing plate 9 is smaller than the entire area of ​​the target area 51aA of the riser pipe 51. In this embodiment, each backing plate 9 is formed in a shape and size that allows it to pass through the manhole 21 (see Fig. 1) of the trunk part 2.

[0026] As shown in FIG. 4, the backing plates 9 are arranged along the outer peripheral surface 51a (outer surface) of the riser pipe 51 so as to cover the entire target area 51aA of the riser pipe 51. Here, the length of the vertical side 9b of the backing plate 9 is set to be equal to or greater than the length of the target area 51aA in the longitudinal direction of the riser pipe 51. In addition, the length of the horizontal side 9a of the backing plate 9 is smaller than the length of the target area 51aA in the circumferential direction of the riser pipe 51. Therefore, the multiple backing plates 9 are arranged only in the circumferential direction of the riser pipe 51. Note that, if the length of the vertical side 9b of the backing plate 9 is smaller than the length of the target area 51aA in the longitudinal direction of the riser pipe 51, the multiple backing plates 9 may also be arranged in the longitudinal direction (up-down direction) of the riser pipe 51.

[0027] The backing plates 9 arranged in the circumferential direction of the riser pipe 51 are fixed to the riser pipe 51 by welding. At least one pair of horizontal sides 9a of each backing plate 9 are joined to the riser pipe 51 by fillet welding. In addition, the vertical sides 9b of the backing plates 9 forming both ends of the backing plates 9 in the circumferential direction of the riser pipe 51 are also joined to the riser pipe 51 by fillet welding. However, when joining all four sides 9a, 9b by welding, some sides are left unwelded in order to release air remaining inside. The vertical sides 9b of the backing plates 9 adjacent to each other in the circumferential direction of the riser pipe 51 may be joined to the riser pipe 51 by, for example, fillet welding. Note that the vertical sides 9b of the backing plates 9 adjacent to each other in the circumferential direction of the riser pipe 51 may not be welded, for example, by simply fitting these vertical sides 9b together. In this case, the vertical sides 9b of the backing plates 9 adjacent to each other in the circumferential direction may be formed, for example, in an uneven shape that fits together.

[0028] Each backing plate 9 is preferably made of a material having high corrosion resistance against the secondary cooling water, such as a Cr-Mo based low alloy or a Ni-based alloy.

[0029] FIG. 5 shows a backing plate 9C formed of a Cr-Mo low alloy. The backing plate 9C shown in FIG. 5 has a main body plate portion 91 made of a Cr-Mo low alloy, and an edge portion 92 made of carbon steel and welded to at least a part of the periphery of the main body plate portion 91. The edge portion 92 made of carbon steel may be provided at a portion of the backing plate 9C to be welded to the riser pipe 51. In the backing plate 9C shown in FIG. 5, only the portions of the backing plate 9C that form a pair of horizontal sides 9a (upper and lower portions of the backing plate 9C) are formed of the edge portion 92 made of carbon steel. Note that the portions of the pair of horizontal sides 9a and the pair of vertical sides 9b (i.e., the entire periphery of the backing plate 9C) may be formed of the edge portion 92 made of carbon steel.

[0030] 6 shows the backing plate 9N made of a Ni-based alloy. The backing plate 9 made of a Ni-based alloy is made of a single material (i.e., only the Ni-based alloy).

[0031] (moisture separator) As shown in Fig. 1, the moisture separator 7 is disposed inside the upper body 2b and above the steam-water separator 5. The moisture separator 7 removes moisture from the steam separated in the steam-water separator 5 to produce a state close to dry steam.

[0032] In the steam generator 1 shown in FIG. 1, the primary cooling water heated by the reactor is sent to the inlet water chamber 6A, circulates through the heat transfer tubes 32 of the heat exchanger section 3, and reaches the outlet water chamber 6B. Meanwhile, the secondary cooling water is supplied from the water supply section 4 to the heat exchanger section 3, passes through the flow passage 35 of the heat exchanger section 3, and rises along the heat transfer tube group 32A. At this time, in the heat exchanger section 3, heat exchange occurs between the high-temperature primary cooling water and the secondary cooling water, and the cooled primary cooling water is returned to the reactor from the outlet water chamber 6B. Meanwhile, the secondary cooling water heated by the primary cooling water rises inside the tube group outer cylinder 31, and is separated into steam and hot water in the steam separator 5. Then, the separated steam is removed of moisture in the moisture separator 7, and is discharged to the outside of the body section 2 through the steam outlet 22, and sent to the turbine generator.

[0033] (Method of reinforcing steam generator) Next, a method for reinforcing a steam generator according to this embodiment will be described. The configuration of the steam generator before reinforcement is the same as the configuration of the steam generator 1 shown in Figures 1 to 4 except for a plurality of backing plates 9. The target to be reinforced in the steam generator reinforcement method is a target area 51aA of the outer circumferential surface 51a of the riser pipe 51 (the outer surface of the steam-water separator 5) with which the secondary cooling water supplied from the water supply section 4 hits.

[0034] In order to reinforce the outer peripheral surface 51a of the riser pipe 51, first, a preparation step is performed in which a plurality of backing plates 9 as exemplified in FIGS. 5 and 6 are prepared outside the torso 2 (for example, in another factory away from the steam generator). In the preparation step, each backing plate 9 is processed into a shape that conforms to the target area 51aA of the outer peripheral surface 51a of the riser pipe 51. Also, in the preparation step, each backing plate 9 is formed into a shape and size that allows it to pass through the manhole 21 (see FIG. 1) of the torso 2. In this embodiment, the length of the vertical side 9b of the backing plate 9 prepared in the preparation step is equal to or greater than the length of the target area 51aA in the longitudinal direction of the riser pipe 51. Also, the length of the horizontal side 9a of the backing plate 9 is smaller than the length of the target area 51aA in the circumferential direction of the riser pipe 51.

[0035] In the preparation step, a backing plate 9C (see FIG. 5) made of a Cr-Mo low alloy or a backing plate 9N (see FIG. 6) made of a Ni-based alloy is prepared. When the backing plate 9C made of a Cr-Mo low alloy is prepared in the preparation step, an edge portion 92 made of carbon steel is joined to the periphery of a main body plate portion 91 made of a Cr-Mo low alloy by welding (e.g., buttering welding) as shown in FIG. When welding the main body plate portion 91 and the edge portion 92, a post-heat treatment is performed depending on the composition of the members.

[0036] After the preparation step, a carrying-in step is performed in which a plurality of backing plates 9 are carried into the interior of the torso 2. In the carrying-in step, a plurality of backing plates 9 are carried into the torso 2 through the manhole 21 of the torso 2. Here, since each backing plate 9 is formed in a shape and size that allows it to pass through the manhole 21, each backing plate 9 can be carried into the interior of the torso 2 easily and reliably.

[0037] After the carrying-in step, a welding step is performed in which the backing plates 9 carried into the body 2 are overlapped and welded to the target areas 51aA of the outer circumferential surface 51a of the riser pipe 51, and aligned along the target areas 51aA. The welding step will be specifically described below.

[0038] In the welding step, first, as shown in FIG. 7, a region (hereinafter, referred to as a welding region 51aB) on the outer circumferential surface of the riser pipe 51 to which the backing plate 9 is to be welded is polished so that the backing plate 9 can be well welded to the riser pipe 51. The welding region 51aB in FIG. 7 is a belt-shaped region extending in the circumferential direction of the riser pipe 51, and two welding regions 51aB are formed at an interval in the longitudinal direction (up-down direction) of the riser pipe 51. These two welding regions 51aB are located on both sides of the target region 51aA in the longitudinal direction of the riser pipe 51. The positions of the two welding regions 51aB correspond to a pair of horizontal sides 9a of the backing plate 9. When the vertical sides 9b of the backing plate 9 are welded to the riser pipe 51, the riser pipe 51 may be formed with a belt-shaped welding region (not shown) extending in the longitudinal direction thereof and corresponding to the vertical sides 9b of the backing plate 9.

[0039] 8, the backing plate 9 is placed on the target area 51aA of the outer circumferential surface 51a of the riser pipe 51, and it is confirmed whether the backing plate 9 is in close contact (surface contact) with the outer circumferential surface 51a of the riser pipe 51 without any gaps. If there is a gap between the backing plate 9 and the outer circumferential surface 51a of the riser pipe 51, the backing plate 9 is pressed against the outer circumferential surface 51a of the riser pipe 51 using, for example, a pressing tool 10 shown in FIG.

[0040] The pressing tool 10 includes a base member 101 and a wedge member 102. The base member 101 is formed in an L-shape and has a facing portion 103 that faces the target area 51aA of the outer circumferential surface 51a of the riser pipe 51 with a gap therebetween when the base member 101 is attached to the riser pipe 51 by welding. The wedge member 102 is sandwiched between the backing plate 9 arranged to overlap the target area 51aA of the riser pipe 51 and the facing portion 103 of the base member 101. By sandwiching the wedge member 102 between the backing plate 9 and the facing portion 103 of the base member 101, the backing plate 9 can be pressed against the outer circumferential surface 51a of the riser pipe 51. This allows the backing plate 9 to be in close contact with the outer circumferential surface 51a of the riser pipe 51 without any gaps. The pressing tool 10 is removed from the riser pipe 51 after the backing plate 9 is welded.

[0041] After it is confirmed that the backing plate 9 is in close contact with the outer circumferential surface 51a of the riser pipe 51 without any gaps, the backing plate 9 is temporarily attached to the riser pipe 51 by welding. The backing plate 9 is temporarily attached to the riser pipe 51 by TIG welding or the like so that short weld beads (spot-shaped weld beads) are arranged at intervals. The backing plate 9 is temporarily attached at least between a pair of horizontal sides 9a of the backing plate 9 and the welded area 51aB of the riser pipe 51 (see FIG. 7). The backing plate 9 may be temporarily attached, for example, between the vertical sides 9b of the backing plate 9 and the corresponding welded area (not shown) of the riser pipe 51.

[0042] After the temporary attachment of the backing plate 9, the backing plate 9 is permanently welded. In the permanent welding of the backing plate 9, the backing plate 9 is welded to the riser pipe 51 by fillet welding or the like so that the weld bead is longer than that in the temporary attachment. In the permanent welding, for example, the backing plate 9 may be welded to the riser pipe 51 by continuous welding in which the entire horizontal side 9a or the entire vertical side 9b of the backing plate 9 is welded. In the permanent welding, for example, the backing plate 9 may be welded to the riser pipe 51 by intermittent welding (tap welding) in which a plurality of linear weld beads are arranged at intervals along the horizontal side 9a or the vertical side 9b of the backing plate 9.

[0043] In this embodiment, the upper horizontal side 9a of the backing plate 9 and the vertical sides 9b of the backing plates 9 forming both ends of the multiple backing plates 9 in the circumferential direction of the riser pipe 51 are welded to the riser pipe 51 by continuous welding. The lower horizontal side 9a of the backing plate 9 is welded to the riser pipe 51 by intermittent welding. Note that the vertical sides 9b of the backing plates 9 adjacent to each other in the circumferential direction of the riser pipe 51 do not have to be welded to the riser pipe 51 by, for example, fitting into each other, or may be welded to the riser pipe 51 by, for example, continuous welding. By joining the upper horizontal edge 9a and vertical edge 9b of the backing plate 9 to the riser pipe 51 by continuous welding, the secondary cooling water discharged from the water supply section 4 can be prevented from entering between the riser pipe 51 and the backing plate 9 even if it flows downward from above the backing plate 9.

[0044] In the welding step, the plurality of backing plates 9 are welded together to cover the entire target area 51aA of the outer circumferential surface 51a of the riser pipe 51. In the welding step, when welding the plurality of backing plates 9, for example, after a given backing plate 9 has been tacked and welded, another backing plate 9 may be tacked and welded, or, for example, after the plurality of backing plates 9 have been tacked, the plurality of backing plates 9 may be welded. When the above-mentioned welding steps are completed, the method for reinforcing the steam generator is completed.

[0045] This method for reinforcing a steam generator can be applied to both a steam generator that has already been used and a steam generator that has not yet been used (is unused). In a steam generator that has already been used, the above-mentioned method for reinforcing a steam generator can be applied to repair a target area 51aA of the outer circumferential surface 51a of the riser pipe 51 that has been thinned due to contact with the secondary cooling water with a plurality of backing plates 9. In a steam generator that has not yet been used (is unused), the target area 51aA of the outer circumferential surface 51a of the riser pipe 51 can be reinforced with backing plates 9 to prevent the target area 51aA from being thinned due to the secondary cooling water.

[0046] According to the steam generator 1 and the reinforcing method for a steam generator of this embodiment, the target area 51aA of the outer circumferential surface 51a of the riser pipe 51 (the outer surface of the steam-water separator 5) is covered by the backing plate 9. This makes it possible to suppress or prevent the secondary cooling water supplied from the water supply section 4 from hitting the target area 51aA of the outer circumferential surface 51a of the riser pipe 51. That is, the target area 51aA of the outer circumferential surface 51a of the riser pipe 51 can be protected from the secondary cooling water. This makes it possible to suppress or prevent the outer circumferential surface 51a of the riser pipe 51 from being thinned due to erosion or corrosion.

[0047] In addition, by providing a plurality of backing plates 9 corresponding to the target area 51aA of the outer circumferential surface 51a of the riser pipe 51, the size of each backing plate 9 can be formed smaller than the target area 51aA. This allows the backing plates 9 to be easily carried into the body 2. In addition, by forming each backing plate 9 small, even if the gap between the target area 51aA of the outer circumferential surface 51a of the riser pipe 51 and the water supply section 4 (particularly the annular water supply pipe 41 and the discharge pipe 42) is narrow, each backing plate 9 can be easily welded to the outer circumferential surface 51a of the riser pipe 51. In other words, the workability of reinforcement is improved, and the target area 51aA of the outer circumferential surface 51a of the riser pipe 51 can be efficiently reinforced.

[0048] Furthermore, in the steam generator 1 and the reinforcing method for a steam generator of this embodiment, the backing plate 9 is formed of a Cr-Mo low alloy or Ni-based alloy having high corrosion resistance against the secondary cooling water. This makes it possible to effectively suppress the backing plate 9 from being thinned due to erosion or corrosion even if the secondary cooling water supplied from the water supply unit 4 hits the backing plate 9 covering the target area 51aA of the outer circumferential surface 51a of the riser pipe 51 for a long period of time.

[0049] Furthermore, according to the steam generator 1 and the steam generator reinforcing method of this embodiment, the backing plate 9 made of Cr-Mo low alloy is configured by welding an edge portion 92 made of carbon steel to at least a part of the periphery of a main body plate portion 91 made of a Cr-Mo based low alloy. As a result, even if the main portion of the backing plate 9 is made of a Cr-Mo low alloy, when welding the backing plate 9 to the outer circumferential surface 51a of the riser pipe 51 in the trunk portion 2, no post-treatment heat treatment is required for the welded portion of the backing plate 9. This point will be described below. In order to weld the Cr-Mo low alloy to the riser pipe 51, it is necessary to perform a post-heat treatment of the welded portion in the torso section 2, which makes it difficult to work in the torso section 2 and to apply the backing plate 9. On the other hand, the above-mentioned post-heat treatment is not required when welding carbon steel to the riser pipe 51. As a result, when welding the edge portion 92 of the backing plate 9, which is made of carbon steel and forms the horizontal side 9a and the vertical side 9b of the backing plate 9, to the outer circumferential surface 51a of the riser pipe 51, the post-heat treatment is not required, which improves workability in the torso section 2 and makes it easy to apply the backing plate 9 to the outer circumferential surface 51a of the riser pipe 51.

[0050] Furthermore, in the steam generator 1 and the steam generator reinforcing method of this embodiment, when the backing plate 9 is made of a Ni-based alloy, pre-heat treatment is not required for the welded portion of the backing plate 9 when welding the backing plate 9 to the outer peripheral surface 51a of the riser pipe 51. This is because pre-heat treatment is not required when welding a Ni-based alloy. As a result, workability within the torso section 2 is improved when welding the backing plate 9 to the outer peripheral surface 51a of the riser pipe 51 within the torso section 2, and the backing plate 9 can be easily applied to the outer peripheral surface 51a of the riser pipe 51.

[0051] Although each embodiment of the present disclosure has been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and design changes and the like that do not deviate from the gist of the present disclosure are also included.

[0052] <Additional Notes> The reinforcing method for a steam generator and the steam generator described in each embodiment can be understood, for example, as follows.

[0053] (1) A method for reinforcing a steam generator according to a first aspect includes a cylindrical body portion extending in a vertical direction, a heat exchange portion provided in a lower portion of the body portion for cooling high-temperature primary cooling water by heat exchange between the primary cooling water and secondary cooling water, a water supply portion provided in the body portion above the heat exchange portion for supplying the secondary cooling water to the heat exchange portion, and a steam-water separator provided in the body portion above the heat exchange portion for separating the secondary cooling water, which is heated by the primary cooling water and rises in the heat exchange portion, into steam and hot water. A method for reinforcing a steam generator, which reinforces a target area on the outer surface of a steam-water separator that is contacted by the secondary cooling water supplied from the water supply section, includes a preparation step of preparing a plurality of backing plates processed into a shape that conforms to the target area of ​​the outer surface on the outside of the body, a delivery step of delivering the plurality of backing plates into the body, and a welding step of overlapping and welding the plurality of backing plates delivered into the body to the target area of ​​the outer surface, and aligning them along the target area of ​​the outer surface.

[0054] According to the above configuration, the target area on the outer surface of the steam-water separator is covered by the multiple backing plates, which can suppress or prevent the secondary cooling water supplied from the water supply unit from hitting the target area on the outer surface of the steam-water separator. In other words, the target area on the outer surface of the steam-water separator can be protected from the secondary cooling water. This can suppress or prevent the outer surface of the steam-water separator from being thinned due to erosion or corrosion.

[0055] Furthermore, by providing a plurality of backing plates corresponding to the target area on the outer surface of the steam-water separator, the size of each backing plate can be made smaller than the target area. This makes it easy to carry the backing plates into the body. Furthermore, by making each backing plate small, even if the distance between the target area on the outer surface of the steam-water separator and the water supply section is narrow, each backing plate can be easily welded to the outer surface of the steam-water separator. In other words, the workability of reinforcement is improved, and the target area on the outer surface of the steam-water separator can be efficiently reinforced.

[0056] (2) In the method for reinforcing a steam generator according to the second aspect, the backing plate is formed of at least a Cr-Mo based low alloy.

[0057] The Cr-Mo low alloy that forms the backing plate has high corrosion resistance against secondary cooling water, so that even if the secondary cooling water supplied from the water supply unit hits the backing plate that covers the target area on the outer surface of the steam-water separator for a long period of time, the backing plate can be effectively prevented from being thinned due to erosion or corrosion.

[0058] (3) In the method of reinforcing a steam generator relating to the third aspect, the backing plate has a main body plate portion made of a Cr-Mo-based low alloy and an edge portion made of carbon steel and welded to at least a portion of the periphery of the main body plate portion.

[0059] According to the above configuration, the edge of the backing plate made of carbon steel can be welded to the outer surface of the steam-water separator, thereby making it possible to attach the backing plate to a target area on the outer surface of the steam-water separator. Here, when welding a Cr-Mo low alloy, a prognostic heat treatment is required for the welded portion, but when welding carbon steel, no prognostic heat treatment is required for the welded portion. As a result, when welding the backing plate to the outer surface of the steam-water separator inside the body, the prognostic heat treatment is not required, improving workability inside the body and facilitating the application of the backing plate to the outer surface of the steam-water separator.

[0060] (4) In the method for reinforcing a steam generator according to a fourth aspect, the backing plate is made of a Ni-based alloy.

[0061] The Ni-based alloy from which the backing plate is made has high corrosion resistance to secondary cooling water, and therefore, even if the secondary cooling water supplied from the water supply unit hits the backing plate covering the target area on the outer surface of the steam-water separator for a long period of time, the backing plate can be prevented from being thinned. Furthermore, by welding a backing plate made of a Ni-based alloy to the outer surface of the steam-water separator, the backing plate can be attached to the target area on the outer surface of the steam-water separator. Here, when welding the Ni-based alloy, no pre-heat treatment is required for the welded portion. As a result, when welding the backing plate to the outer surface of the steam-water separator inside the body, the pre-heat treatment is not required, improving workability inside the body and facilitating the application of the backing plate to the outer surface of the steam-water separator.

[0062] (5) In a method of reinforcing a steam generator relating to a fifth aspect, the body portion has a manhole for entering and exiting the body portion, and the backing plate is formed in a shape and size that allows it to pass through the manhole.

[0063] By forming the backing plate into a shape and size that allows it to pass through the manhole, the backing plate can be easily and reliably transported into the body.

[0064] (6) A steam generator according to a sixth aspect comprises a cylindrical body extending in a vertical direction, a heat exchange section provided in a lower part of the body for cooling high-temperature primary cooling water by heat exchange between the primary cooling water and secondary cooling water, a water supply section provided in the body above the heat exchange section for supplying the secondary cooling water to the heat exchange section, a steam-water separator provided in the body above the heat exchange section for separating the secondary cooling water heated by the primary cooling water in the heat exchange section and rising therefrom into steam and hot water, and a plurality of backing plates welded to a target area of ​​the outer surface of the steam-water separator that is hit by the secondary cooling water supplied from the water supply section and aligned along the target area of ​​the outer surface.

[0065] According to the above configuration, the target area on the outer surface of the steam-water separator is covered by the multiple backing plates, which can suppress or prevent the secondary cooling water supplied from the water supply unit from hitting the target area on the outer surface of the steam-water separator. In other words, the target area on the outer surface of the steam-water separator can be protected from the secondary cooling water. This can suppress or prevent the outer surface of the steam-water separator from being thinned due to erosion or corrosion.

[0066] Furthermore, by providing a plurality of backing plates corresponding to the target area on the outer surface of the steam-water separator, the size of each backing plate can be made smaller than the target area. This makes it easy to carry the backing plates into the body. Furthermore, by making each backing plate small, even if the distance between the target area on the outer surface of the steam-water separator and the water supply section is narrow, each backing plate can be easily welded to the outer surface of the steam-water separator. In other words, the workability of reinforcement is improved, and the target area on the outer surface of the steam-water separator can be efficiently reinforced. [Explanation of symbols]

[0067] 1. Steam generator 2. Torso 3 Heat exchange section 4 Water supply section 5 Steam water separator 9 Backing Plate 21 Manhole 51a Outer surface (outer surface) 51aA Target Area 91 Main body plate 92 Edge

Claims

1. A cylindrical body portion extending in the vertical direction; a heat exchange section provided in a lower portion of the body section for exchanging heat between high-temperature primary cooling water and secondary cooling water to cool the primary cooling water; a water supply section provided in the body section above the heat exchange section and configured to supply the secondary cooling water to the heat exchange section; a steam-water separator provided in the body portion above the heat exchange portion and configured to separate the secondary cooling water, which is heated by the primary cooling water in the heat exchange portion and rises, into steam and hot water; A steam generator comprising: A method for reinforcing a steam generator, comprising: reinforcing a target area of ​​an outer surface of the steam-water separator that is contacted by the secondary cooling water supplied from the water supply section, the method comprising: A preparation step of preparing a plurality of backing plates on the outside of the body, the backing plates being shaped to conform to the target area of ​​the outer surface; A carrying step of carrying a plurality of the backing plates into the body portion; a welding step of overlapping and welding the plurality of backing plates brought into the body to the target areas of the outer surface and arranging them along the target areas of the outer surface; having The method for reinforcing a steam generator includes forming the backing plate from at least a Cr-Mo based low alloy steel.

2. A cylindrical body portion extending in the vertical direction; a heat exchange section provided in a lower portion of the body section for exchanging heat between high-temperature primary cooling water and secondary cooling water to cool the primary cooling water; a water supply section provided in the body section above the heat exchange section and configured to supply the secondary cooling water to the heat exchange section; a steam-water separator provided in the body portion above the heat exchange portion and configured to separate the secondary cooling water, which is heated by the primary cooling water in the heat exchange portion and rises, into steam and hot water; A steam generator comprising: A method for reinforcing a steam generator, comprising: reinforcing a target area of ​​an outer surface of the steam-water separator that is contacted by the secondary cooling water supplied from the water supply section, the method comprising: A preparation step of preparing a plurality of backing plates on the outside of the body, the backing plates being shaped to conform to the target area of ​​the outer surface; A carrying step of carrying a plurality of the backing plates into the body portion; a welding step of overlapping and welding the plurality of backing plates brought into the body to the target areas of the outer surface and arranging them along the target areas of the outer surface; having The method for reinforcing a steam generator, wherein the backing plate has a main body plate portion made of Cr-Mo based low alloy steel and an edge portion made of carbon steel and welded to at least a portion of the periphery of the main body plate portion.

3. A cylindrical body portion extending in the vertical direction; a heat exchange section provided in a lower portion of the body section for exchanging heat between high-temperature primary cooling water and secondary cooling water to cool the primary cooling water; a water supply section provided in the body section above the heat exchange section and configured to supply the secondary cooling water to the heat exchange section; a steam-water separator provided in the body portion above the heat exchange portion and configured to separate the secondary cooling water, which is heated by the primary cooling water in the heat exchange portion and rises, into steam and hot water; A steam generator comprising: A method for reinforcing a steam generator, comprising: reinforcing a target area of ​​an outer surface of the steam-water separator that is contacted by the secondary cooling water supplied from the water supply section, the method comprising: A preparation step of preparing a plurality of backing plates on the outside of the body, the backing plates being shaped to conform to the target area of ​​the outer surface; A carrying step of carrying a plurality of the backing plates into the body portion; a welding step of overlapping and welding the plurality of backing plates brought into the body to the target areas of the outer surface and arranging them along the target areas of the outer surface; having The method for reinforcing a steam generator, wherein the backing plate is made of a Ni-based alloy.

4. The body portion has a manhole for accessing the body portion, 4. The method for reinforcing a steam generator according to claim 1, wherein the backing plate is formed in a shape and size that allows it to pass through the manhole.

5. A cylindrical body portion extending in the vertical direction; a heat exchange section provided in a lower portion of the body section for exchanging heat between high-temperature primary cooling water and secondary cooling water to cool the primary cooling water; a water supply section provided in the body section above the heat exchange section and configured to supply the secondary cooling water to the heat exchange section; a steam-water separator provided in the body portion above the heat exchange portion and configured to separate the secondary cooling water, which is heated by the primary cooling water in the heat exchange portion and rises, into steam and hot water; a plurality of backing plates that are overlapped and welded to a target area of ​​an outer surface of the steam-water separator where the secondary cooling water supplied from the water supply section hits, and that are arranged along the target area of ​​the outer surface; Equipped with The backing plate of the steam generator is made of at least a Cr-Mo based low alloy steel.

6. A cylindrical body portion extending in the vertical direction; a heat exchange section provided in a lower portion of the body section for exchanging heat between high-temperature primary cooling water and secondary cooling water to cool the primary cooling water; a water supply section provided in the body section above the heat exchange section and configured to supply the secondary cooling water to the heat exchange section; a steam-water separator provided in the body portion above the heat exchange portion and configured to separate the secondary cooling water, which is heated by the primary cooling water in the heat exchange portion and rises, into steam and hot water; a plurality of backing plates that are overlapped and welded to a target area of ​​an outer surface of the steam-water separator where the secondary cooling water supplied from the water supply section hits, and that are arranged along the target area of ​​the outer surface; Equipped with The backing plate of the steam generator has a main body plate portion made of Cr-Mo based low alloy steel, and an edge portion made of carbon steel and welded to at least a part of the periphery of the main body plate portion.

7. A cylindrical body portion extending in the vertical direction; a heat exchange section provided in a lower portion of the body section for exchanging heat between high-temperature primary cooling water and secondary cooling water to cool the primary cooling water; a water supply section provided in the body section above the heat exchange section and configured to supply the secondary cooling water to the heat exchange section; a steam-water separator provided in the body portion above the heat exchange portion and configured to separate the secondary cooling water, which is heated by the primary cooling water in the heat exchange portion and rises, into steam and hot water; a plurality of backing plates that are overlapped and welded to a target area of ​​an outer surface of the steam-water separator where the secondary cooling water supplied from the water supply section hits, and that are arranged along the target area of ​​the outer surface; Equipped with The steam generator, wherein the backing plate is formed of a Ni-based alloy.

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